This invention generally relates to slider-operated flexible zippers for use in reclosable pouches, bags or other packages of the type in which perishable material, such as foodstuff, may be stored.
Reclosable fastener assemblies are useful for sealing thermoplastic pouches or bags. Such fastener assemblies often include a plastic zipper and a slider. Typically, the plastic zippers include a pair of interlockable fastener elements, or profiles, that form a closure. As the slider moves across the profiles, the profiles are opened or closed. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure elements, etc.
Conventional slider-operated zipper assemblies typically comprise a plastic zipper having two interlocking profiles and a slider for opening and closing the zipper. In one type of slider-operated zipper assembly, the slider straddles the zipper and has a separating finger at one end that is inserted between the profiles to force them apart as the slider is moved along the zipper in an opening direction. The other end of the slider is sufficiently narrow to force the profiles into engagement and close the zipper when the slider is moved along the zipper in a closing direction.
Other types of slider-operated zipper assemblies avoid the use of a separating finger. For example, U.S. Pat. No. 5,809,621 discloses a slider-operated zipper assembly wherein one zipper profile has a pair of handles that cooperate with the slider. As the slider is moved in an opening direction, the handles are squeezed together to disengage the profiles. In U.S. Pat. No. 5,442,838, a slider-operated zipper assembly is disclosed wherein the zipper profiles are engaged and disengaged in the course of a “rolling action”. This “rolling action” is described as being achieved through cooperation between flanges on the profiles and shoulders which project inwardly from the arms of the slider. U.S. Pat. No. 6,047,450 discloses a zipper comprising a pair of mutually interlockable profiled structures. The first profiled structure comprises an interlocking element on a surface directed toward the second profiled structure and an integral base directed away from the second profiled structure. Likewise, the second profiled structure comprises an interlocking element on a surface directed toward the first profiled structure and an integral base directed away from the first profiled structure. Additionally, portions of the two profiled structures form a fulcrum about which the profiled structures may be pivoted out of engagement when lower edges of the bases are forced towards each other.
In the case of sliders having a separating finger or post, it is usually necessary to have the finger or post extend into the product side of the package. Since the zipper halves are relatively rigid, they do not conform to the shape of the post and a gap is left between the post and the point where the zipper halves are fully mated. This gap creates a potential for liquid and gas leakage from or into the package. From this standpoint, sliders without separating fingers or posts are an improvement.